I have several loaner 8830's (Sprint is the provider) that I give to clients for overseas travel. I'm aware of the GSM capability requirement for use outside of the US. In the past I've sent them out with the BB's 'network' setting to 'Global'. When set to 'Global' my client indicates that his internet and email (ie. data) is functioning but he is unable to make any calls. I've had them change the netowrk setting to 'GSM' This fixes the cell phone issue but now they don't get emails or internet (no data)

I don't know how much this will help since I'm on VZW...they had me make sure I kept it on 'Global' and had me do a battery pull for a full minute when I landed...since I could make and receive calls but not emails. Once I did that, the BB registered on the network and 'GPRS' came up in the top right...and it was good to go.

My guess is that a simple battery pull will do the trick, regardless of the Global vs. GSM setting. The other thing that I found helpful was to scan for networks, and explicitly select a network with a strong presence in the area that I'm visiting.